The subject matter disclosed herein relates to the art of mechanical anchors and, more particularly, to a screw anchor for attaching objects or structures to a concrete base material.
Mechanical fasteners for securing objects to a base material such a concrete, brick, block, and the like are available in a wide variety of sizes and thread profiles. Conventional anchor screws include both symmetric and asymmetric thread profiles. Symmetric thread profiles include thread forms having a sharp apex defined by an upper angled surface that is identical to a lower angled surface. Asymmetrical thread profiles include thread forms having a sharp apex defined by an upper angled surface that is dissimilar to a lower angled surface. One such type of asymmetrical thread profile is a buttress thread. In a buttress thread, load bearing thread faces are perpendicular to the axis of the screw. Buttress threads enable fasteners to withstand very high axial thrusts in one direction. However, when used in substrates having relatively low tensile strength properties such as concrete, brick, and block, buttress threads are less effective.